It is commonly recognized that by means of various kinds of sensors several signals in electrical form may be measured on the surface of the skin, such as:                electrical curve of heartbeat that is the ECG signal        electrical activity of muscles that is the EMG signal        electrical curve of brain function that is the EEG signal        conductivity of the surface of the skin        respiration rate        percentage of fat        intracellular and extracellular fluid balance in the body        
In sensories today in use, two or several electrodes are typically used, between which an electrical signal describing the potential difference is measured and which signal is transmitted for further processing in an electronic device. Measuring electrodes mentioned earlier are either separate electrodes to be attached on the skin one by one or electrode groups comprising several electrode surfaces, or various constructions placed on outfits, belts, bands or similar to be worn by a person, in which case several individual electrode surfaces in those are situated on the skin in defined places and in defined order.
Electrodes in clinical measurements are fastened with glue or a suction cup on the skin and the quality of a signal is secured by means of a special gel or similar improving conductivity. Outside clinical environment, for instance, during a physical exercise these kinds of electrodes have proved to be unpractical despite their reliability.
Sensories so-called heart rate monitors meant for monitoring a physical exercise are based on recognizing heartbeat by means of a sensor placed on the chest. The sensor is typically a solid elastic band by shape (a sensor band) or an elastic textile belt (a sensor belt) or an outfit, to which conductive electrode constructions have been integrated. Most conductive electrode surfaces in sensor bands are fastened to a frame part, by means of which the electrodes are then placed against the skin. Typically, the frame part is not able to stick to the skin by itself but it needs a separate fastening part, for instance, an elastic band or belt.
Electrodes in a sensor band are usually made of electro conductive plastics. The band is fastened on the chest by means of an elastic ribbon, the tightness of which is adjustable. As the plastic electrode surface is of solid material, there will by nature appear a wet space maintaining conductivity between the skin and the electrodes. Especially, during long performances and while sweating a lot, the band, however, slips away from its place or it may feel uncomfortable or cause abrasion. In addition, various disturbances are easily connected to measuring of a signal since the band as a solid construction is not elastic enough during motions normally included in the performance.
In a textile sensor band or similar outfit, the electrodes have been made of conductive textile or of conductive fibres, which are integrated to isolating textile in other way. While the textile construction in itself is permeable, on the outside of the textile electrode a separate layer holding moisture must be attached, for instance, by sewing, in which case sufficient conductivity is created between an electrode and the skin. The electrode constructions gathered in this way are attached to a belt or an outfit, for instance, by sewing. The belt or the outfit is put on in which case electrodes in them are placed on the chest to points where they stay in place as well as possible from the measuring point of view also during physical exercise. Especially, in outfit-type solutions, in places where the electrodes are, there will be thicker areas in the outfit fabric where the extra thickness due to the electrode textile and the layers holding moisture and their seams stiffen the fabric hindering the wearability of the outfit and causing disturbance for its part in the measurement. In addition, the most advantageous shape of textile electrode surfaces and moisturizing layers is usually square, as that shape is the most convenient to cut and to sew in manufacturing phase. A square shape is, however, not always the best shape in terms of measuring the actual signal, as, for instance, free and flexible shapes fitting as good as possible to the body anatomy are needed in measuring muscle activities.
Measuring heart rate during swimming or some other activity in water is especially complicated. Water may pass between the sensor band and the skin during swimming or in some other water activity, in which case impurities in the water (among other things salt, chlorine etc.) cause a short circuit between the electrodes of the band or some other means, in which case the measuring signal is disturbed. In addition, the flow resistance of water tends to move the band on the chest downwards the body, in which case the band is inconvenient to wear and causes friction slowening swimming.
Outfits on market with integrated electrodes in them have usually been made by adding conductive fibres or areas made of conductive material already in the manufacturing phase of the fabric or the outfit. Conductive fibres may be sewed among the own fibres of the ready fabric or they may be knitted or weaved straight to the structure of the fabric in the manufacturing phase. In other words, conductive material is either conductive fibre-like material or material is of fibre the surface of which has been made conductive. These fibres are then integrated to an outfit. Conductive material needs a supporting construction to be able to be attached to an outfit. These conductive fibres must also be made to a fibre-like form, as conductive fibre-like raw material does not exist. Electrode areas on outfits are also made by cutting off normal fabric from a ready outfit and fitting fabric made of conductive material or some other material to the area made in this way. Implementation of all outfits mentioned earlier requires special design and/or extra working phases, which increase manufacturing costs and which also partly changes the original usability characteristics of the outfit.
The object of the invention is to provide a sensory for measuring signals on the surface of the skin and a method for producing sensory, with the use of which disadvantages related to present methods are eliminated. Especially, the object of the invention is to provide sensory, which meets the shape and elasticity demands important from the signal-measuring point of view, and while using which the measuring electrodes stay in their place and in reliable contact also during a long-term measuring, heavy perspiration and various movements. In addition, sensory enables reliable and easy-to-use measurements also on users differing from each other by anatomy. Furthermore, the object of the invention is to provide a method, with the use of which sensory is able to be realized simply, advantageously and reliably.